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Lighting for Parking Garages

Parking garages are often considered dim, dirty and dangerous places that are concrete blights on our urban landscapes. Fortunately, this image is rapidly changing as parking garages become more upscale. Architects, owners and designers are beginning to realize that a better-looking garage with quality lighting will not only improve the environment, but will attract more customers.

The Visual Environment

Many factors will affect the visual environment within a parking garage, including vertical illumination, the light source and glare. Facility designers must achieve a balance between these factors to create a comfortable environment that attracts customers and makes them feel safe and secure.

The first question designers often face is how much light is needed within the facility. The Illuminating Engineering Society (IES) offers specific recommendations, as shown in Table 1. The values suggested represent the lowest levels that should be used within a parking structure.

Today, many designers and owners have increased these levels to achieve better uniformity ratios and provide a safer visual environment. Many facilities are designed to 5 footcandles (horizontal and vertical) with uniformity ratios near 5:1. To assure that the garage meets your expectations as far as the lighting is concerned, you may want to survey other facilities in your area before establishing the lighting guidelines.

Table 1:

  Minimum Horizontal
(measured in foot-candles)
Horizontal Uniformity
Maximum/ Minimum
Minimum Vertical*
(measured in foot-candles)
Basic      
  1 10:1 .5
Ramps      

Day

2 10:1 1

Night

1 10:1 .5
Entrance Areas      

Day

50   25

Night

1 10:1 .5
Stairways      
  2   1
*Measured facing the drive aisle at 5 feet above the parking surface at the point of the lowest horizontal illuminance.

In designing the lighting system, it is important to determine where in the garage the light is needed and how that light should be measured. Often, designers focus on the horizontal light levels when the vertical footcandle levels are actually more important.


To determine where the light is needed, you must first determine what visual task is being performed within the task area. Within most parking garages, drivers must be able to see in front of them to safely maneuver a car through the aisles and into the parking spaces. Pedestrians must be able to see oncoming traffic and between cars. They must also be able to identify other people.


If obstacles exist within the area, both drivers and pedestrians must be able to perceive the objects in order to avoid them. They can do this only when they can see the front or vertical surface of the object.

Besides the quantity of light, the quality of the illumination is important. What type of light will provide the best environment—and what are the tradeoffs that must be made to achieve that environment?

Three types of light sources are typically used in parking structures: metal halide, high-pressure sodium, and fluorescent. Induction light sources have also gained popularity in recent years. When deciding which source is best for the application, you must consider the color, lamp life, efficiency and cost. Table 2 shows how these sources compare. Each lamp has its own unique advantages.

Table 2:

  Metal Halide High Pressure Sodium Fluorescent Induction
Typical wattage 175 150 32 (T-8) 85
Color (CRI) 65-75 Low 20’s 75-85 80+
Lamp Life (hours) 10,000 24,000 20,000 100,000
Efficiency
(lumens / watt)
85 100 90 70
Initial Cost Medium Low Lowest High
Comments Offers good color & visual effect. This is a commonly used lamp. Poor color, but offers the most economic life cycle cost. Best color, but has a low lumen package & operates poorly in cold weather. Best life, but is new unproven lamp technology that is expensive.


Fixture Considerations

Once the lighting criteria are in place, the next step is to consider the lighting fixtures and how they will impact the visual environment. Fixture design and placement will affect not only the visual environment but the initial and life cycle costs of the project.

Three types of high intensity discharge (HID) fixtures are typically used in parking garage structures: cutoff, semi cutoff and refractor. When deciding which type of fixture will best suit the application, you must consider such factors as glare, vertical illumination and the cavern effect, which can occur in structures with dark ceilings.

Glare—which affects people’s ability to see—occurs when a point in the field of view is significantly brighter than the ambient light level. All HID fixtures will combat glare if the fixture is properly designed. However, there is a tradeoff. Cutoff fixtures will reduce glare but will decrease the uniformity and vertical illumination. In addition, these fixtures tend to contribute to the cavern effect, which will make the garage feel darker.

A semi cutoff fixture will eliminate the cavern effect by aiming the light onto the ceiling. With this type of fixture, however, vertical illumination will suffer if the luminaire is not properly designed
A refractor type luminaire will provide the greatest level of vertical illumination and will create the feeling of an open environment. However, the risk of glare can be high if the fixture is not properly designed or the lamp wattage is too high.

Of course, no two applications will have the same requirements. In general, my personal recommendation is to use a refractor type luminaire with a long and narrow distribution that will push the light into the parking spaces and minimize glare in the drive aisle. By utilizing this type of luminaire with a metal halide lamp, you will create a totally luminous, comfortable environment with high vertical footcandles.

As a designer, you will want to insert your own personal influence into each job. But before you make any decisions, you may want to examine real world applications using the fixtures and lamps you are considering. By applying the above criteria, you will create a bright environment that makes customers feel secure and encourages them to use your facility.

 

The Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts boosted security for students with a 100-watt high-pressure sodium system mounted at 13 feet. The luminaires have a 360-degree light disbursement, which makes the lighting very uniform.

 

Luminaires with a symmetric refractor illuminate the 1400-space employee parking garage at Intel Corporation in Rio Rancho, New Mexico. The luminaires are mounted at 9 1/2 feet, set into the double T construction of the concrete ceiling.

This before and after photo shows the new prismatic glass luminaires (left) installed within the busy parking garage at O’Hare International Airport in Chicago. The fixtures on the right are the wide-distribution downlight units—with metal reflectors—that were originally used to light the facility.



 
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